In a retrospective study, treatment with ergocalciferol (vitamin D2) was associated with a significantly reduced risk of vascular access dysfunction in this population (OR 0.32, 95% CI 0.13 to 0.75, P<0.01), Karina Vasquez, MD, of the University of Texas Health Science Center, and colleagues reported during a poster session at the National Kidney Foundation meeting here.

Vascular access for dialysis can be particularly problematic for patients with diabetes, who are already at risk for worse vascular outcomes. These complications are usually caused by venous neointimal hyperplasia near the graft or fistula.

Most cells in the neointimal lesion are smooth muscle cells or precursors thereof, and they have an enzyme that converts 25 hydroxyvitamin D (vitamin D2) to its active metabolite, 1,25 dihydroxyvitamin D (vitamin D3). This feature may enable vitamin D supplementation to suppress proliferation of vascular cell smooth muscle, the researchers explained.

"If there is a property that can affect problems with neointimal hyperplasia, and vitamin D plays a role in that, we can probably see a change," Vasquez told MedPage Today.

She and her colleagues reviewed data from an electronic health record that spanned several dialysis centers in San Antonio. In all, 256 dialysis patients (mean age 57) were treated with ergocalciferol, a vitamin D2 supplement; 155 of these patients had type 2 diabetes.

Patients were classified as deficient if they had levels of 25OHD (vitamin D) below 15 ng/mL, and were deemed insufficient at 15 to 30 ng/mL.

Diabetes patients in the sample were older, and had a higher prevalence of coronary artery disease and obesity than patients who were not diabetic (P<0.001). They were also more likely to have 25OHD deficiency and insufficiency (P=0.003).

Vasquez and colleagues found that, contrary to much prior work, having diabetes wasn't associated with an increased risk for venous-arterial dysfunction -- but they faulted the low number of diabetic patients in the study population for the finding.

However, there were improvements in vascular access for patients with diabetes, they found. Taking vitamin D2 was associated with a significant reduction in the risk of vascular access dysfunction (OR 0.32, 95% CI 0.13 to 0.75, P<0.01).

Vasquez noted that they used vitamin D2 in the trial -- instead of the active form of vitamin D3 -- because the cells affected in vascular access problems have an enzyme that converts vitamin D2 to vitamin D3. However, some patients may have also received vitamin D3 at some other point in their care, she said, so future work will look to separate out that potential confounder.

The study was also limited by its observational nature and a small sample size.

Still, Vasquez and colleagues concluded, treating vitamin D deficiency or insufficiency with ergocalciferol in diabetes patients can diminish problems with vascular access. They noted, however, that their finding should be confirmed in future randomized controlled trials.

Tamim Naber, MD, a nephrologist at MedAmerica Group in Ventnor, N.J., who was not involved in the study, said reducing vascular access is just one of the many advantages, including improvements in heart disease, offered by treating diabetic patients with vitamin D.

He cautioned, however, that he'd like to see "more randomized clinical trials for greater accuracy," and warned that if clinicians treat their patients with more vitamin D, they need to be on the lookout "for changes in phosphorus and calcium, since treatment with vitamin D can increase phosphorus and calcium."

The researchers reported no conflicts of interest.

Reviewed by F. Perry Wilson, MD, MSCE Instructor of Medicine, Perelman School of Medicine at the University of Pennsylvania and Dorothy Caputo, MA, BSN, RN, Nurse Planner

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